HORNBEAM (Carpinus betulus), a member of a small genus of trees of the natural order Corylaceae. The Latin name Carpinus has been thought to be derived from the Celtic car, wood, and pin or pen, head, the wood of hornbeams having been used for yokes of cattle (see Loudon, Ency. of Pl. p. 792, new ed. 1855, and Littré, Dict. ii. 556). The common hornbeam, or yoke-elm, Carpinus betulus (Ger. Hornbaum and Hornbuche, Fr. charme), is indigenous in the temperate parts of western Asia and of Asia Minor, and in Europe, where it ranges as high as 55° and 56° N. lat. It is common in woods and hedges in parts of Wales and of the south of England. The trunk is usually flattened, and twisted as though composed of several stems united; the bark is smooth and light grey; and the leaves are in two rows, 2 to 3 in. long, elliptic-ovate, doubly toothed, pointed, numerously ribbed, hairy below and opaque, and not glossy as in the beech, have short stalks and when young are plaited. The stipules of the leaves act as protecting scale-leaves in the winter-bud and fall when the bud opens in spring. The flowers appear with the leaves in April and May. The male catkins are about 1½ in. long, and have pale-yellow anthers, bearing tufts of hairs at the apex; the female attain a length in the fruiting stage of 2 to 4 in., with bracts 1 to 1½ in. long. The green and angular fruit or “nut” ripens in October; it is about ¼ in. in length, is in shape like a small chestnut, and is enclosed in leafy, 3-lobed bracts. The hornbeam thrives well on stiff, clayey, moist soils, into which its roots penetrate deeply; on chalk or gravel it does not flourish. Raised from seed it may become a tree 40 to as much as 70 ft. in height, greatly resembling the beech, except in its rounder and closer head. It is, however, rarely grown as a timber-tree, its chief employment being for hedges. “In the single row,” says Evelyn (Sylva, p. 29, 1664), “it makes the noblest and the stateliest hedges for long Walks in Gardens or Parks, of any Tree whatsoever whose leaves are deciduous.” As it bears clipping well, it was formerly much used in geometric gardening. The branches should not be lopped in spring, on account of their tendency to bleed at that season. The wood of the hornbeam is white and close-grained, and polishes ill, is of considerable tenacity and little flexibility, and is extremely tough and hard to work — whence, according to Gerard, the name of the tree. It has been found to lose about 8% of its weight by drying. As a fuel it is excellent; and its charcoal is much esteemed for making gunpowder. The inner part of the bark of the hornbeam is stated by Linnaeus to afford a yellow dye. In France the leaves serve as fodder. The tree is a favourite with hares and rabbits, and the seedlings are apt to be destroyed by mice. Pliny (Nat. Hist. xxvi. 26), who describes its wood as red and easily split, classes the hornbeam with maples.

The American hornbeam, blue or water beech, is Carpinusamericana (also known as C. caroliniana); the common hop-hornbeam, a native of the south of Europe, is a member of a closely allied genus, Ostrya vulgaris, the allied American species, O. virginiana, is also known as iron wood from its very hard, tight, close-grained wood.